function slide(n){i = document.getElementsByTagName('div');a='active';h='hidden';l='left';r='right';e='';z=i.length;
c=c+n;
if(c<0){c=c+z;}
i[(c+z-3) % z].className=e;
i[(c+z-2) % z].className=h+l;
i[(c+z-1) % z].className=l;
i[c % z].className=a;
i[(c+1) % z].className=r;
i[(c+2) % z].className=h+r;
i[(c+3) % z].className=e;
}
